The importance of the orientation of the polymer membrane hydrophone in the acoustic field

The performance of spot poled PVDF membrane hydrophones was examined. It was found that the sensitivity of the hydrophone is markedly dependent on the spatial polarization distribution. In addition, the experimental data show there can be a significant difference between the voltage sensitivities measured in the same hydrophone probe depending on which electrode is actually facing the acoustic source. The measurements carried out in the frequency range 1–20 MHz indicate that this difference, while negligible below 2 MHz may exceed 1.6 dB at higher frequencies. The theoretical model allowing comprehensive characterization of the membrane hydrophone probe to be predicted was developed and experimentally verified. The results of this work indicate that in the critical applications such as the quantitative field measurements or ultrasonic dosimetry, the membrane hydrophone's electrode exposed to the ultrasound source should be carefully identified.